• Keitaro Matsukawa, Takashi Kato, Yoshiyuki Yato, Hiroshi Sasao, Hideaki Imabayashi, Naobumi Hosogane, Takashi Asazuma, and Kazuhiro Chiba.
• Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan.
• Spine. 2016 Jul 15; 41 (14): E851-E856.

Study DesignRetrospective study evaluating cranial facet joint violation (FJV) by pedicle screws.ObjectiveThe aim of the study was to determine the incidence and risk factors of FJV following screw placement via cortical bone trajectory (CBT).Summary Of Background DataCBT is a new minimally invasive technique for lumbar pedicle screw insertion that minimizes muscle dissection. Inserting a screw from a more caudal entry point can reduce iatrogenic damage to the cranial facet joint; however, no previous reports exist describing the incidence of FJV secondary to the CBT technique.MethodsWe reviewed 202 consecutive patients who underwent lumbar pedicle screw instrumentation using CBT from October 2011 to June 2015. Postoperative CT scans were obtained to determine the degree and incidence of FJV. Clinical and imaging data were analyzed to clarify the risk factors of FJV. The detailed positions of the proximal screws were also investigated and compared between the FJV and non-FJV groups.ResultsThe incidence of FJV by the proximal screws was 11.8% (48/404), with no occurrence of intra-articular FJV. Multiple logistic regression analysis revealed that age >70 years, vertebral slip >10%, and adjacent facet joint degeneration (Pathria's grade 2 or 3) were independent factors significantly affecting FJV. There were statistically significant differences between the FJV and non-FJV groups in the facet-screw distance (3.2 ± 1.0 vs. 8.1 ± 2.3 mm, P < 0.01), the cranial angle (25.8 ± 6.3° vs. 29.9 ± 7.6°, P < 0.01), and the lamina-screw head distance (5.6 ± 1.6 vs. 6.4 ± 1.9 mm, P < 0.01).ConclusionLumbar pedicle screw placement via CBT would reduce FJV; however, special care should be taken in patients with age >70 years, vertebral slip >10%, and facet degeneration.Level Of Evidence3.

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